Cholera is a highly infectious disease caused by a vibrio organism. Although the infection can be spread by person-to-person contact, the most common source is contaminated water supplies, the contamination usually arising from sewage containing the organism. Generally, cholera is controlled by administering suitable drugs to the person suffering from the disease. However, there are many advantages to treating exposed persons prophylactically and treating the contaminated water to prevent or greatly reduce the incidence of the disease.